The present invention relates to a method and a device for controlling the drive train of a vehicle.
In motor vehicles having drive train management, the drive torque and the drive power can be set by electronic control of the engine and transmission. In order to provide the drive torque desired by the driver and the corresponding drive power, an output torque from the engine and a set speed ratio from the transmission is required. It is essential in this context to make an appropriate determination of this desired torque and the desired power.
German Patent Application No. 196 93 324 A shows an engine control system in which a relative engine output torque is provided via a characteristic map as a function of the engine r.p.m. and the position of the gas pedal activated by the driver of the vehicle. Considering the possible torque interval of the engine at the current operating point, a setpoint value is determined for the engine torque. This method is related only to engine power control, however, not to drive train control, in which all the components forming the drive train, such as engine, clutch, torque converter, and transmission, are considered.
European Patent No. 0 557 299 describes a method in which an absolute value for the drive torque is formed from a characteristic map as a function of the gas pedal position and the vehicle speed.
European Patent No. 0 406 615 describes that the driving activity and the driving type of the driver can be inferred, among other things, from the activation of the gas pedal.
An object of the present invention is to optimally adapt the drive torque to be set or the drive power to be set to the driver""s preference and to the prevailing driving condition during drive train control.
The present invention is based on a method and a device for controlling the drive train of a vehicle having a gas pedal activated by the driver of the vehicle. In this context a setpoint value is formed for the drive torque or a setpoint value for the drive power as a function of the position of the gas pedal. Then the drive train is controlled in a such a way that the drive torque or the drive power is set as a function of the setpoint value formed. The core of the invention determines an interval with pre-definable interval limits. The interval limits represent maximum and minimum values for the drive torque to be set or the drive power to be set. The setpoint values are formed as a function of the determined interval according to the present invention. The basis for optimal adaptation of the drive torque to be set or the drive power to be set to the driver""s preference and to the prevailing driving condition is made possible by the drive train control according to the present invention.
In an advantageous embodiment of the present invention, the lower interval limit is determined as a function of: the minimum power or minimum torque that can be currently generated by the vehicle engine the instantaneous torque ratio of the transmission, the operating condition of a transformer in the drive train and/or the operating condition of a clutch in the drive train, in particular a transformer bridging clutch.
The upper interval limit can be determined as a function of: the maximum power or maximum torque that can currently be generated by the vehicle engine and/or the prevailing efficiency of the components forming the drive train.
It is particularly advantageous to measure a speed quantity representing the longitudinal vehicular speed and to determine the upper interval limit and/or the lower interval limit as a function of the measured speed quantity.
Furthermore, in an advantageous embodiment of the present invention, a driver type quantity is determined representing the driving behavior of the driver. The setpoint value for the drive torque or the setpoint value for the drive power is then formed as a function of the determined driver type quantity.
The position of the gas pedal can be compared with a pre-definable lower threshold value and/or a pre-definable upper threshold value. With this embodiment of the present invention, the setpoint value for the drive torque or the setpoint value for the drive power is formed as a function of this comparison. In this context a speed quantity is measured representing the longitudinal vehicular speed and at least one threshold value is pre-determined as a function of the measured speed quantity.
Furthermore, in the previously described embodiment, a negative setpoint value (coastdown operation) can be set when the position of the gas pedal drops below the lower threshold value. When the position of the gas pedal is within the threshold value, then a setpoint value within the interval limits is set (normal operation). When the position of the gas pedal exceeds the upper threshold value, then a setpoint value is set that exceeds the upper interval limits (kickdown operation).